Pen



FIG. 1 is a front perspective view illustrating my design for a pen;

FIG. 2 is a front view of my design;

FIG. 3 is a left side view of my design;

FIG. 4 is a top view of my design;

FIG. 5 is a right side view of my design;

FIG. 6 is a bottom view of my design; and,

FIG. 7 is a rear view of my design. 

The ornamental design for a pen, as shown and described. 